The present invention relates to sealed bearings for small angle applications and pertains particularly to an improved bearing seal for use on rotary actuators for rigid disk magnetic data storage devices.
Hard disk storage devices have a head to disk interface that is very sensitive to and cannot tolerate contaminants. Such storage devices have moving parts, such as actuators and arms that are mounted on lubricated ball or roller bearings. Pressure and temperature changes within the storage devices cause air flow through the bearings. This air flow picks up and carries small particles of grease, and evaporated organic particles which can reach and deposit on the recording disk surfaces. These contaminants can interfere with the performance of the carefully designed lubricant that is applied thereto.
In accordance with the present state of the art, side shields or rubber seals are provided to impede the transport of grease out of the bearing cartridge. However, in order to allow rotation of the spindle, spacing is provided between the inside diameter of the shield (or rubber seals) and the outside of the inner race of the bearing, which allows contaminants to pass through in three ways:
1. Grease vapors diffuse through this gap at all times. PA1 2. Turbulence induced by high speed accessing convects vapors, and aerosols through the gap. PA1 3. Pressure difference between the top and bottom of the bearing cartridge causes axial flow which carries aerosols and vapors of the grease.
The form factor of the disk drive imposes such severe constraints of the allowable axial length of seals that no known seals can be used. For example, bellows type seals have been used in certain applications where space is not a factor. See for example, U.S. Pat. No. 3,700,297 issued Oct. 24, 1972 to Fickenwirth, et al. for an aircraft control surface. Other examples of the prior art are illustrated in U.S. Pat. No. 4,208,060 issued Jun. 17, 1980 to St. Lauret, Jr; U.S. Pat. No. 3,489,019 issued Jan. 13, 1970 to Giegerich; and U.S. Pat. No. 2,469,114 issued May 3, 1949 to Hofst.
Accordingly, it is desirable that compact highly effective seals that allow small angles of oscillation be available.